1. Field of the Invention
This invention relates to a method and apparatus for editing digital signals which are recorded on a record medium, and is more particularly directed to a method and apparatus wherein digital signals such as PCM-encoded audio signals are edited electronically in an insert or assemble mode of electronic editing.
2. Description of the Prior Art
There have been proposed PCM recording and reproducing arrangements to record and play back an audio signal as a digital signal. In such arrangements an audio signal is converted to a digital signal by pulse code modulation (PCM) and then is recorded and later played back. In a typical studio recording, it is desirable to employ electronic editing for combining an already-recorded signal with a new signal. Generally, the PCM recording and reproducing arrangement carries out electronic assembly or insertion editing. One example of such electronic editing is disclosed in application Ser. No. 116,401 filed Jan. 29, 1980, and having a common assignee.
If the above electronic editing is performed on a recorded signal, errors will always be expected to be produced at the edit points, i.e., at the starting points and stopping points of the recording operation. When an error is produced only once in a predetermined length of the record medium, it can be corrected by using an error correcting code commonly recorded with the digital signal. However, if the editing is repeatedly carried out so that many edit points occur in a brief span, a corresponding number errors may be generated in that span, with the result that the errors are no longer correctable. Consequently, when the digital signal is played back, portions thereof where multiple editing has taken place will often be accompanied by a distinct audible "click". In order to combat this undesirable effect, the starting and stopping points of recording should be controlled during electronic editing, so that uncorrectable errors are prevented.